Rotigotine is the International Non-Proprietary Name (INN) of the compound (−)-5,6,7,8-tetrahydro-6-[propyl-[2-(2-thienyl)ethyl]-amino]-1-naphthalenol having the structure shown below

Rotigotine is a non-ergolinic D1/D2/D3 dopamine agonist that resembles dopamine structurally and has a similar receptor profile but a higher receptor affinity.
In contrast to other non-ergolinic dopamine agonists, Rotigotine has significant D1 activity, which may contribute to a greater physiological action.
In contrast to ergolinic compounds, Rotigotine has a very low affinity for 5 HT2B receptors and thus a low risk of inducing fibrosis.
Actions on non-dopaminergic receptors (such as 5-HT1A agonism and A2B antagonism) may contribute to other beneficial effects, such as antidyskinetic activity, neuroprotective activity and antidepressive effects.
Rotigotine is disclosed as active agent for treating patients suffering from Parkinson's disease (described in WO 2002/089777), Parkinson's plus syndrome (described in WO 2005/092331), depression (described in WO 2005/009424) and the restless-legs syndrome (described in WO 2003/092677) as well as for the treatment or prevention of dopaminergic neuron loss (described in WO 2005/063237).
Known pharmaceutical compositions containing Rotigotine comprise a transdermal therapeutic system (TTS) (described in WO 99/49852), a depot form (described in WO 02/15903), an iontophoretic device (described in WO 2004/050083) and an intranasal formulation (described in WO 2005/063236).
Each of the above cited publications is incorporated by reference in its entirety herein.
One crystalline form of Rotigotine is already known and will hereinafter be designated as polymorphic form (I).
Surprisingly a further crystalline form of Rotigotine (polymorphic form (II)) has now been identified and found to show a greatly enhanced thermodynamic stability and an improved shelf-life as well as a cubic crystal shape that represents an advantage over the needle like particles of polymorphic form (I) regarding its handling properties such as filtering properties, flowability, electrostatic behaviour, etc.
The discovery of a second crystalline Rotigotine polymorph is especially astonishing as Rotigotine is a commercial drug that has been known since the mid eighties and has been well investigated over the past decade. Furthermore, no indication for the presence of a second crystalline Rotigotine polymorph was observed in a first polymorphism screening that was earlier conducted during formulation development.